1. Field of the Invention
The present invention relates to a process for image forming which uses a photosensitive member having an amorphous carbon layer as an outermost surface layer, and predetermined transfer paper.
2. Description of the Related Art
In electrophotographic image forming apparatuses, organic members have been widely used as photosensitive members for forming electrostatic latent images and toner images, because the organic photosensitive members are superior to inorganic photosensitive members in view of sanitation and manufacturing costs. However, in general, the organic photosensitive members have a low surface hardness. Even if they initially had good chargeability and photosensitivity, these good characteristics may be impaired due to scratching of the surfaces and/or abrasion of the photosensitive layers which are caused by friction with sheets of transfer paper, cleaning members, developer and/or others during repeated copying operations.
In recent years, in accordance to demand for high-speed operation and high quality image resolution of copying machines and printers, it has been desired to provide a photosensitive member having a good durability. For this reason, there has been proposed a photosensitive member including a protective layer formed of an amorphous carbon layer over the surface of the organic photosensitive member. The amorphous carbon layer is very hard, and use of the surface protective layer formed of such film can provide the organic photosensitive member having good durability without impairing the electrostatic characteristics of the base photosensitive layer.
However, the photosensitive member having the surface protective layer formed of the amorphous carbon layer has such a disadvantage that the image resolving ability reduces as it is repetitively used.
The reason for this is that loading material such as talc, kaolin and clay as well as other electrolytes such as metallic oxide, which are component of paper powder of the transfer paper used in the conventional electrophotography, adhere to and accumulate on the surface of the amorphous carbon layer, which reduces a surface resistance of the photosensitive member.
On the other hand, the photosensitive member having the low surface hardness, i.e., the photosensitive member, which does not have the amorphous carbon layer as the outermost surface, does not have a significant problem even if the electrolyte contained in the transfer paper adheres thereto, because the electrolyte is scraped off when the surface of the photosensitive member is shaved off due to the friction with the member such as the cleaning member. Conversely, the surface resistance of the photosensitive member having a high surface hardness reduces when it is repetitively used, because the electrolyte adhered to the surface of the amorphous carbon layer is not scraped off and thus accumulates thereon. The amorphous carbon layer has a high surface activity, and the electrolyte itself adhered thereto is ionized by ozone and ion generated during the charging operation, which further reduces the surface resistance of the photosensitive member.
Therefore, it is necessary to eliminate or remarkably reduce the electrolyte contained in the transfer paper. The inventors have studied in various aspects how to overcome the above-noted disadvantages and have found that the content of the electrolyte component, which is liable to be ionized, in the transfer paper can be indirectly measured by the pH-value measuring method JIS-P-8133 defined by the Japanese Industrial Standards. Based on these studies and findings, the present invention has been developed.